The current invention relates to a means whereby an object can be rendered more readily adaptable from a first form suitable for a first use to a second form suitable for a second use, and to an adhesive, in particular, but not necessarily exclusively, a hot aqueous solvent switchable adhesive comprising or essentially consisting of a plasticized esterified expanded starch obtained by at least expanding starch to provide an expanded starch, esterification of the expanded starch to provide an esterified expanded starch, and plasticization of the esterified expanded starch to provide a plasticized esterified expanded starch. In particular, the current invention relates to a method of using such hot aqueous solvent switchable adhesive as the agent for allowing the adaptability of the object to be achieved, and the use and preparing of such adhesive for use in various objects to render the same more readily recyclable as a result of the adaptability. In particular, the invention is directed towards floor coverings such as carpet, carpet tiles or rugs with a first form for use as the floor covering or part thereof and a second form in which at least one of the components of the object is more readily available to be recycled.
Floor coverings are widely used and examples of these are carpet tiles, carpets or rugs (hereinafter referred to in a non limiting manner as “carpets or carpet tiles”). Carpets or carpet tiles are the floor covering of choice in many households and businesses in the world but unfortunately carpet or carpet tiles have a limited lifespan and must eventually be replaced, with the resultant used carpet waste generally being sent to landfill.
These vast quantities of carpet waste have a negative impact on the environment, and the recycling of materials, like nylon and bitumen, comprised in the carpet is currently limited. The quantity of used carpet or carpet tiles discarded thus amounts to significant economical losses in potentially reusable materials.
It is therefore not surprising that, in order to limit impact on the environment and reuse some of the materials in carpet or carpet tiles, recycling has in recent years become attractive. Recycling carpet or carpet tiles, however, is difficult because the components that are used to build up carpet or carpet tiles are chemically and physically diverse.
Carpets or carpet tiles, typically comprise a traffic-bearing or wear face surface on a primary backing such as a fibrous face surface (hereinafter referred to as a carpet face layer), which has been woven, needle-punctured, fusion-bonded or otherwise secured to a primary backing layer or sheet, and a backing layer which includes a surface to which is bonded one or more layers of solid or foam backing material.
A solid backing material typically comprises thermoplastic-type materials like a polyvinyl chloride backing material or a bitumen or atactic polypropylene backing layer. For example, carpet or carpet tiles can consist of a carpet face layer of yarn (or carpet fibre), and a backing layer which includes any or any combination of bitumen, EVA (ethylene-vinyl acetate), APP (atactic polypropylene), hot melts, urethanes, and SBR (styrene-butadiene)) and/or polypropylene; and an adhesive composition which attaches the filaments of the carpet face layer (yarn; carpet face fibres) to the backing layer. In addition, other components like a glass backing, or a primary backing fabric may be present (see FIG. 1).
A widely applied adhesive to bind the filaments within the carpet face layer together and bind the carpet face layer to for example the bitumen backing layer of the carpet or carpet tiles is latex, in particular carboxylated styrene butadiene copolymer latex, also referred to as SBR-latex. Such materials have been used as carpet or carpet tiles backing adhesives for many years.
To recycle carpet or carpet tiles, the carpet face layer, adhesive and backing layer should typically be separated from each other in order to be reprocessed into new products or to be chemically recycled. Unfortunately, recycling of the components of carpets or carpet tiles are hindered due to the residual presence of adhesive, for example SBR latex, when the layers have been mechanically separated under great tensile stresses. In other words, adhesive might still be present both in the yarn of the carpet face layer and in/on the backing layer, thereby providing contaminated materials not suitable for proper reuse.
Various methods for better separation of the components of carpet or carpet tiles have been proposed, either by mechanical means or by adjusting the build-up of the components of the carpet or carpet tiles. For example, U.S. Pat. No. 5,240,530 discloses a method of grinding carpet and washing in a water bath to allow the various materials of the carpet to be separated by density. This method will however not solve the problem of residual presence of the adhesive attached to for example the yarn or the backing.
U.S. Pat. No. 5,230,473 describes a method for disintegrating, separating and segregating the base component materials of carpet, which comprises loosening and debonding a latex/filler binder system from the secondary backing by application of pressurized fluids and chemical solutions. This method has however the drawback that high amounts of energy have to be spent in a process using vast amounts of chemicals, while in addition the problem of residual presence of the adhesive in/on the yarn/fabric is not solved satisfactory.
U.S. Pat. No. 5,840,773 describes a method of extracting nylon from carpet waste by dissolving it in an alcohol-water agent. This method uses large quantities of organic solvents. Another example is U.S. Pat. No. 5,889,142 which discloses dissolving nylon from carpet in a caprolactam-water mixture.
Another approach is to modify the adhesive, allowing it to be more easily separated. Although various modified (latex-based) adhesives for carpet tiles have been described, in general these are not easily separated or removed from carpet fibres.
For example, U.S. Pat. No. 4,191,799 discloses an adhesive prepared from a copolymer of styrene, butadiene, and a carboxylic acid-containing monomer, combined with an olefin-grafted mineral oil extender; U.S. Pat. No. 3,546,059 discloses an adhesive prepared from styrene, butadiene, vinylidene chloride, and a functional monomer that improves the bonding of the fibres of the composite material.
U.S. Pat. No. 6,610,769 discloses adhesives for use in carpet and that employs a copolymer dispersion of styrene, butadiene, and a mixture of ethylenically unsaturated carboxylic acid monomers and latex.
JP 6343542 describes the use of a water-soluble adhesive that can be decomposed or dissolved when the adhesive is immersed into water or hot water. Water-soluble adhesives and copolymer emulsion adhesives are used alone or in combination.
However, none provide a satisfactory solution to the problem discussed above with respect to efficient recycling of objects such as carpet or carpet tiles, and none provide a satisfactory adhesive that can be suitably used in a carpet or carpet tiles that can be recycled.
It would thus be advantageous to develop a more environmental-friendly adhesive suitable for use in, for example, carpets or carpet tiles, that has long durability, resistance to blistering, has good adhesive properties, retains strength when wet, but that can easily be removed without use of vast amounts of organic compounds or shear forces or other mechanical and environmentally unfriendly chemical treatments, and allows for the removal and/or separation of a backing layer from the carpet face fibres and efficient recycling of both the carpet face layer and the backing layer.